1. Chapter 7 Human Health and Environmental Toxicology

2. Overview of Chapter 7 Human Health Environmental Pollution and Disease
Health issues in developed countries
Health issues in developing countries
Environmental Pollution and Disease
Environmental Contaminants
Endocrine Disrupters
Determining Health Effects of Pollutants
Ecotoxicology
Risk Assessment

3. Human Health Two indicators of human health
Life Expectancy
Infant Mortality
Vary greatly between countries
Developed countries
Developing countries

4. Health Issues in Highly Developed Countries
By many measures- health is good in these countries
Average life expectancy
Men – 76 years
Women – 82 years
Leading causes of death in US
Cardiovascular disease
Cancer
Chronic Obstructive Pulmonary Disease (of the lungs.

5. Health Issue in Highly Developed Countries
Premature deaths caused by lifestyle
Poor diet
Lack of exercise
Smoking
Obesity is big problem
Body Mass Index (BMI)
(Weight X 740)/ (height (in))2
18.5 is underweight
18.5 – 24.9 is healthy
25-29 is overweight
>30 is obese

6. Health Issues in Developing Countries
Biggest problems
Malnutrition, unsafe water, poor sanitation
Life Expectancy
Overall is 65 years
Very poorest developing countries = 45 years
Childhood mortality is high (18% of deaths)
Diarrheal disease
Malnutrition
Malaria
AIDS/HIV

7. Emerging and Reemerging Diseases
Emerging Disease - not previously observed in humans
Usually jumps from animal host
Ex: AIDS, lyme disease, West Nile Virus
Reemerging Disease- existed in the past and are recently increasing in incidence
Ex: tuberculosis, yellow fever, malaria

8. Reasons for Emergence/Reemergence
Evolution of disease so it can move to human host
Evolution of antibiotic resistance in disease
Urbanization and overcrowding
Increased pop. of elderly- susceptible to disease
Pollution and environmental degradation
Growth in international travel and commerce
Poverty and social inequality

9. Environmental Pollution and Disease
Often difficult to link pollutants to their effects on people
Persistence
Bioaccumulation
Biomagnification

10. Persistence
A characteristic of certain chemicals that are extremely stable and may take many years to be broken down into simpler forms by natural processes
Synthetic chemicals
DDT
Natural decomposers (bacteria) have not evolved a way to break it down

11. Bioaccumulation
The buildup of a persistent toxic substance in an organism’s body, often in fatty tissues
Synthetic chemicals do not metabolize well
They remain in the body for extended periods of time.

12. Biomagnification
The increased concentration of toxic chemicals in the tissues of organisms that are at higher levels in food webs
Diagram is example of biomagnification of DDT

13. Endocrine Disrupters
A chemical that mimics or interferes with the actions of the endocrine system in humans and wildlife
i.e. It effects the ability of the hormones in the organisms to function properly
Examples include: PCBs, Dioxins, Heavy metals (lead and mercury), DDT
Animals exposed to these chemicals have altered reproductive development and are often sterile

14. Endocrine Disrupters and Humans
Infertility and hormonally related cancers are increasing
Phthalates have been implicated as potential endocrine disrupters
Cannot make a link between endocrine disrupters and human illness

15. Determining Health Effects of Pollutants
Toxicology is the study of the effect of toxicants on the human body
Acute toxicity – adverse effects occur within a short period after exposure to toxin
Chronic toxicity – adverse effects occur some time after exposure or after prolonged exposure.

16. Toxicity Toxicity measured by dose and response LD50 and LC50
Dose: amount that enters that body of an exposed organism
Response: the amount of damage caused by a specific dose
LD50 and LC50
Lethal dose to 50% of the test organisms
Smaller the LD50 the more lethal the chemicl
Determined for all new synthetic chemicals.

18. Toxicity ED50 Dose-Response Curve
Effective dose to 50% of test organisms
ED50 causes 50% of the population to exhibit whatever effect is under study
Dose-Response Curve
Illustrates the effect of different doses on a population
Threshold Level
Maximum dose with no measurable effects.

19. ED50

20. Children and Chemical Exposure
Children more susceptible to chemicals
Weigh less than adults
Bodies are still developing
Play on the floor & lawns
Put everything in their mouth.
Diagram
Children in foothills not exposed to pesticides
Children in valley were exposed

21. Identifying Cancer Causing Substances
Toxicologist
Dose rats with varying levels of chemicals to see if they develop cancer
Difficult to extrapolate results to humans
Epidemiologists
Look at historical exposure of groups of humans
See if exposed group have increased cancer rate

22. Chemical Mixtures
Most studies look at one chemical, but humans tend to be exposed to chemical mixtures
Ex: automobile exhaust
Chemical Mixtures interact by
Additivity
Synergy
Antagonism
These studies are expensive and take a while to complete

23. Chemical Testing

24. Ecotoxicology Dilution Paradigm is not valid
“Dilution is the solution to pollution”
Boomerang Paradigm is accepted
“What you throw away can come back and hurt you”
Ecotoxicology
The study of contaminants in the biosphere and their harmful effects on ecosystems
Helps policy makers determine costs and benefits of industrial and technological “advances”
And how they often adversely effect ecosystems

25. Case Study: The Ocean
Land based nutrient and pollution runoff into ocean is affecting microorganisms
Ex: Red Tide
Red pigmented poisonous algal blooms
Toxins kill off fish and make humans sick

26. Risk Assessment
Risk- probability that a particular adverse effect will result from some exposure or condition
We assess risk daily with four steps
Hazard Identification
Dose Reponse assessment
Exposure assessment
Risk Characterization

27. Risk Assessment

28. Risk Assessment

29. Ecological Risk Assessment
Difficult to assess because effect occur at wide range of scales
Individual plants and animals
Ecological communities over wide regions
Human-induced environmental stressors also range greatly
Good to bad
Acceptable to unacceptable
There is a need to quantify risks to the environment